Guide roll for filaments

ABSTRACT

This invention provides a guide roll for filaments as used in apparatuses in which the draw-twisting, draw-winding, false twisting or heat treatment of the synthetic filaments and the like are carried out, and this guide roll is particularly devised to meet the requirements of high speed operation. Again, it can be used under conditions of elevated temperature and high humidity. Heretofore, radial ball bearings have been used in the guide rolls of low speed rotation, but to meet the demands for an increase in the production in recent years guide rolls equipped with fluid bearings are now being used in view of their low torque and ability to endure its high speed operation. This invention concerns a guide roll equipped with this type of fluid bearing and is one whose performance has been enhanced by specifying as to its basic factors, with a mathematical formula, as a result of detailed observations and repeated experimentation, the numerical values involved in its designing, and also through elaborate works in the detailed parts of the fluid bearing, by eliminating the points which might become causes for trouble. Thus, the guide roll according to the present invention not only meets the conditions for high speed operation but also can maintain its high performance.

United States Patent 1 1 Takenaka et a1.

[ GUIDE ROLL FOR F ILAMENTS [75] Inventors: Yoshisuke Takenaka; Hideki Aoyama, both of lwakuni, Japan {73] Assignee: Teiiin Limited, Osaka, Japan 22 Filed: Sept. 15, 1972 [21] Appl. No.: 289,316

[30] Foreign Application Priority Data Nov. 26, 1971 Japan 46/110976 Apr. 7, 1972 Japan 47/34907 [56] References Cited UNITED STATES PATENTS 11/1962 Quade et a1. 308/D1G. 1

3/1968 Voorhies 9/1970 Christiansen 2/ 1972 Bird 2/1972 Bird 308/107 Primary ExaminerAllen N. Knowles Atmrm' v Leonard W. Sherman, Edwin A. Shalloway et al.

[451 Aug. 21, 1973 ABSTRACT This invention provides a guide roll for filaments as used in apparatuses in which the draw-twisting, drawwinding, false twisting or heat treatment of the synthetic filaments and the like are carried out, and this guide roll is particularly devised to meet the requirements of high speed operation Again, it can be used under conditions of elevated temperature and high humidity. Heretofore, radial ball bearings have been used in the guide rolls of low speed rotation, but to meet the demands for an increase in the production in recent years guide rolls equipped with fluid bearings are now being used in view of their low torque and ability to endure its high speed operation. This invention concerns a guide roll equipped with this type of fluid bearing and is one whose performance has been enhanced by specifying as to its basic factors, with a mathematical formula, as a result of detailed observations and repeated experimentation, the numerical values involved in its designing, and also through elaborate works in the detailed parts of the fluid bearing, by eliminating the points which might become causes for trouble. Thus, the guide roll according to the present invention not only meets the conditions for high speed operation but also can maintain its high performance.

8 Claims, 9 Drawing F igures l' I 3 68 2 |L-' |Q L- 12 PATENTEDAUEZI 1975 3753517 sum 2 BF 2 P K m? ABSOLUTE GUIDE ROLL FOR FILAMENTS This invention relates to a guide roll which is conjointly used with the apparatuses that are used in the manufacturer of synthetic fibers and the like, e.g., draw-twisting machines, the draw-winding machines, false twisting machines or filament heat-treatment machines. For instance, this guide roll is used in the following manner. In manufacturing the synthetic fibers, the freshly spun, undrawn filaments are usually submitted to drawing and heat treatments to enhance their properties. In this case, the drawing is usually carried out by running the filament between a low speed feed roll and a draw roll having a higher speed than said feed roll. It is desired in this case that the ratio of the filament speed around the feed roll to the speed around the draw roll be maintained constant. That is, the foregoing condition is highly important for obtaining filaments having uniform properties. For maintaining the speed ratio constant, as above described, guide rolls were heretofore provided adjunctly in the vicinities of respectively the feed and draw rolls, and the filament being treated is wound around these rolls several times before being sent to the following steps of such as twisting or winding.

The guide roll usually is small and light in weight, its diameter being 20 50 millimeters. It is rotatably mounted on a shaft with a light rotating torque by means of two radial ball bearings, one end of the shaft being affixed to the machine frame, and torque is imparted to the roll by the traveling filament. In the case of the speeds with which the filaments were treated higher to the speed of the guide roll was of the order of 5000 15,000 rpm, a relatively low rotational speed. Hence, the torque required for starting the guide roll did not cause any difficulty in stringing up the filament. Further, the yarn properties were not impaired by the reaction of the torque imparted to the guide roll by the traveling filament.

While the function of the guide roll is as hereinabove described, with the recent advance in the art and in the trend towards high speed production, there has been a marked enhancement in the speed of the production and treatment of filaments, with the consequence that the rotation of the guide roll, whose speed, as previously noted, was 5000 15,000 rpm, is now required to be at least 50,000 rpm. In a guide roll of such a high speed, the bearing is readily damaged if it is a radial ball bearing. For instance, seizure of the bearing takes place frequently. Again, another draw-back is its relatively great torque. Hence, it was found that the conventional radial ball bearing was unsuitable for use with the guide roll that rotates at such high speeds. In consequence, the fluid bearing, e.g., an air bearing, has been adopted. That is to say, a method in which pressurized air is passed about the journal surface, and the stream of air is caused to function as a bearing. As prior arts, there are U. S. Pat. Nos. 3,374,039 and 3,527,510. In both patents the bearing portion comprises a porous sleeve inserted in the journal clearance, into which sleeve pressurized air is introduced. In general, in the case of the bearing using a porous sleeve, the amount of fluid consumed is less than the other types, e.g., the hearing which uses orifices. ln addition, since abnormal vibrations due to unbalance is prevented, the discharge of air from the exhaust orifices provided in roll body is readily accomplished. However, at the present state of the art, i.e., where the precision processing of such porous materials as, for example, the sintered metals has not been established as yet, the employment of this type of material is very difficult. Hence, though its consumption of air is great, the fluid bearing which uses orifices is more practical. This latter type of bearing is disclosed in Japanese Utility Model Publications Nos. 37533/71 and 37537/71. While these clearly illustrate air bearings, they are not inventions relating to the air bearing itself but are rather inventions concerning the accessory conditions.

Now, while the air bearing is well known, as a practical matter, there are no data at all at present to which reference can be made in designing such an air bearing. As already noted, the guide roll, which is of a diameter of 20 50 millimeters, is usually mounted rotatably with a light rotating torque to a shaft, the one end of which shaft is affixed to the machine frame. However, there are not guiding literature whatsoever concerning such matters as the introduction of the pressurized air, the passage for said air and its discharge. We set up the following objects and worked for the perfection of the present invention.

The first object resides in obtaining a stable air bearing having a greater load capacity per unit amount of air consumed.

The second object resides in obtaining a guide roll for filaments, which possesses stability in respect of the following point. The guide roll using an air bearing, as previously noted, undoubtly is improved in its ability to withstand operation at high speeds, heat resistance and lower torque. There is however the drawback that there is a tendency to the body of the guide roll setting up an oscillatory phenomenon in the axial direction when the guide roll part or fittings are subjected to an impact, or as a result of the guide roll being subjected to a load in the axially direction by means of the filament that has been wound about the guide roll in helical fashion. The object in this case is to solve this drawback and provide a stable guide roll.

The third object of the invention resides in providing solutions to the following problems. The air bearing is essentially readily affected greatly by external conditions. For instance, when filaments and like enter the bearing clearance at the time the filament is being strung up, seizure of the bearing takes place instantaneously to cause not only the breakage of the filament but also results in the bearing itself becoming no longer usable. The solution of this point must be achieved. Again, when the filament has been subjected to an excessive load by means of other shafts during the treatment of the filament, or in the case whre the broken filament gets twisted about between the main roll and the guide roll, it is well known from experience that in these cases the filament, which makes several turns about the roll, tend to shift to the rear part of the roll as a result of the pitch of the filament becoming irregular. In case such as this, the chances of the filament entering the bearing clearance of the air bearing increase to cause various troubles such as described above. This also must be solved.

As indicated above, we engaged in extensive researches-with a view to effectively achieving the foregoing objects. As a result, we found that the foregoing objects of the invention could be achieved by an air bearing designed such as to satisfy the following relationship as to the various values involved in its design, and thus the present invention was perfected.

Accordingly, the present invention is directed to a guide roll for filaments comprising a roll body fitted rotatably about a shaft, said shaft being provided with orifices through which pressurized air is introduced to form between said roll body and said shaft an air film by which the roll body is supported, characterized in that the air bearing is so designed that the various values involved in its design are chosen such as to satisfy the following relationship wherein n is the total number of orifices for the introduction of the pressurized air, with the limitation that n 6,

d is the diameter (mm) of the orifices for introducing the pressurized air,

Ps is the pressure (kg/cm absolute) at which the pressurized air is fed, with the limitation that Ps C is the clearance (mm) between the roll body and the shaft in the radial direction, with the limitation that C 10 X 10*,

D is the outside diameter (mm) of the shaft, and

L is the sum of the distances (mm) from the several orifices to thepressurized airdischarge outlet measured in the axial direction, provided that when there is no pressurized air discharge outlet between adjacent orifices, the distance between said orifices is not included.

The value obtained by the formula, log n'd-L/Ps'C 'D, will hereinafter be referred to as the F value.

The invention will be more fully understood from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a section view illustrating a guide roll for filaments in accordance with the present invention; FIGS. 2, 3 and 4 being respectively sectional views taken along lines ll II, III Ill and 1V IV of FIG. 1; FIG. 5 is sectional view illustrating another embodiment of the invention; FIG. 6 being a sectional view taken along line VI VI of FIG. 5; FIG. 7 is a sectional view showing a still another embodiment of the invention; FIG. 8 being a sectional view taken along line VIII VIII of FIG. 7; and FIG. 9 is a graph showing the relationship between Ps and F.

Referring to the drawings, reference numeral 1 is a cylindrical roll body of the filament guide roll, while 2 is a shaft about which the roll body 1 is rotatably fitted to form a clearance 8 between the shaft and the roll body. The shaft 2 is provided with an air passage 5 through its axial center for the introduction of the pressurized air, and branching from the air passage 5 are provided in the shaft 2 orifices 6 from whence the pressurized air is introduced to the clearance 8 to form therein an air film by which the roll body 1 is supported. At the proximal portion of the shaft 2 there is formed integrally thereof a flange 3, while at the other end of the shaft 2 there is screwably attached a flange 7 to the threaded portion 4 of the shaft 2. Thus, there are formed clearances 9 between the ends of the roll body 1 and the inner walls of the flanges 3 and 7, from which the pressurized air is discharged in jet fashion. The shaft 2 is also provided with recessed portions 10 at portions of the shaft intermediately of the orifices 6, the communication between these recessed portions 10 and with the outside being achieved by the provision of holes 11, whereby a part of the pressurized air is discharged to the outside. The flanges 3 and 7 are also provided with orifices 12, which are disposed in the flanges 3 and 7 at positions on an extention line from the air film formed by the clearance between the roll body 1 and the shaft 2. The orifices 12 are also provided for discharging the pressurized air. The flanges 3 and 7 are further provided with sleeves 14, which are so formed such as to envelope the ends of the roll body 1 and by projecting axially of the roll body form clearances between themselves and the roll body 1. The sleeve 14 may be provided at the flange 3 only.

While modifications of the embodiment described above are conceivable, there naturally are imposed various limitations when it is intended to obtain, for example, a greater load capacity per unit amount of air consumed. For instance, such factors as the pressure Ps at which the pressurized air is to be fed, the clearance C in the axially direction between the roll body and the shaft (as indicated by numeral 8 in FIG. 1), the total number n of the orifices 6 for introducing the pressurized air, the diameter d of the foregoing orifices 6, the outside diameter of the shaft 2 and the length L of the air passage provided in parallel to the axial center must be considered. Furthermore, since these factors do not function independently of each other but are mutually closely interrelated, it was conceived to collect together several sets of these factors which were related to each other. First, the throttle resistance at the orifice in the air bearing was considered. As factors participating in this, d (orifice diamter), n (total nuber of orifices) and L (length) can be named. Thus, the combination lid]. is set up. Next, as thethrottle resistance at the air film, Ps (pressure at which the pressurized air is fed), C (the clearance between the roll body and shaft in the axial direction) and D (the outside diameter of the shaft) can be named. The other set PsC -D was set up with these factors. On the basis of these combinations of factors, the formula ndL/PsC D was hypothesized. It is readily conceivable that the foregoing formula is intimately related to the function of the air bearing. We came to the conclusion that the foregoing formula was a suitable criterion by which to judge the performance of an air bearing. Next, when actual calculations were made, since the calculated values became numerals of great magnitude, it was decided to use the logarithmic value to the base 10. As a result, F log (nd'L/Ps'C -D) was adopted. This F value was investigated with a view to finding its most suitable range. It was decided to carry out the determination of the range for the F value in the following order. First, various types of air bearings were made and these were submitted to various tests to determine their performances. From the experimental data obtained, the several F values were calculated, and these values were plotted, distinguishing between those which were good and those which were poor in their performances. The range in which were scattered the F values obtained from those air bearings giving good showings was chosen. in consequence. it was found that the bearings whose performances were good were those satisfying the relationship 2 F 4.5.

In deciding on the foregoing relationship 2 F 4.5 the following matter was considered. That is, in determining as to whether the air bearing was satisfactory or not, the following calculation was made.

R W/Q where R is the load capacity per unit amount of air consumed (kg-min/Nl),

W is the radial load capacity (kg) and Q is the amount of air consumed (NI/min).

In the foregoing method of calculation, an R value of greater than 0.04 is to be preferred. When the R value is 0.04 or less, the load capacity is relatively small as compared with the amount of air consumed, and hence the efficiency of the bearing is very poor. The performance of the air bearing of the present invention was judged for the most part on the basis of the foregoing value. Part of the results of measurements made for determining the range of F are shown in FIG. 9. In the figure the pressure of the air used is represented as abscissa and and F value is represented as ordinate. The bearings tested were of the same type in which values of n, d, L and D were constant but the value of C was varied. The values of C and the reference numerals in the figure correspond as follows:

C (a) Reference numeral 120 (D 100 70 so 30 1 5 Example 1 2 9 In FIG. 9, the bearing as hereinafter indicated, was unsatisfactory in its performance. The F value in this case was 5.01. Next, bearings and were also unsatisfactory in their performances. In these cases the F values were 1.96 and 1.94, respectively. The per formances of the all of the other bearings in FIG. 9 were found to be satisfactory.

Thus, from the results obtained from the foregoing experiment it was decided to adopt for the present invention the following relationship:

2 log (.n'dL/PsC -D) 4.5.

According to our experiments, we found that when the relationship between the various values n, d, L, Ps, C and D involved in the design of the bearing as expressed by the formula log n-d'LlPs'C 'D becomes 2 or less, there was a decline in the load resistance per unit amount of air consumed. On the other hand, when log n'd'L/Ps'C 'D becomes 4.5 or more, a pronounced unbalance between the throttle resistance at the orifices 6 and the throttle resistance at the air film occurs to cause a metal-to-metal rubbing contact and with the radial load capacity becoming virtually zero to render the bearing unserviceable.

On the other hand, even though a choice of the values n, d, L, Ps, C and D are made such that the relationship 2 log n-d-L/Ps-C -D 4.5 is satisfied, if the total number of orifices for introducing the pressurized air is n 6, the pressure of the air film used as the bearing becomes negative to render the bearing instable and susceptible to the so-called lockup phenomenon such as to cause a metal-to-metal rubbing contact. Further, when the pressure Ps at which the pressurized air is fed is less than 3 (kg/cm absolute), it becomes difficult to obtain stably a load capacity sufficient for use as a guide roll. Since, in this case, the guide roll is extremely weak in coping with the fluctuations in the pressure at which the pressurized air is fed or fluctuations in the load imposed on the roll, its reliability as a roll for treating high speed filaments declines to make it unsuitable for use in high speed operations. While it is undesirable for the clearance C between the roll body 1 and shaft 2 in the radial direction to be excessively great, there is also a limit to its smallness. For instance, from the standpoint of the processing precision that can be achieved by the present state of the art, it is extremely difficult to make this clearance less than 10 X 10 (mm). There would be decline in the yield at the time of the manufacture of the roll, or the interchangeability of the roll body 1 and the shaft 2 should suffer. Hence, it would be economically disadvantageous, and thus such a small clearance cannot be adopted as a practical matter.

In the invention guide roll, as shown in FIG. 1, the flanges 3 and 7 at the ends of the guide roll are provided with sleeves l4 axially of the roll. The provision of such sleeves l4 prevents the filament being treated from entering the clearance 9 at, say, the time the filament is being strung up. Further, even at those times when the filament breaks between a roll and the guide roll, and the filament shifts towards the rear end of the roll as a result of the filament pitch becoming irregular, the filament does not enter the clearance 9. Hence, a very stable guide roll for filaments is obtained. Further, in the present invention, the recessed portions 10 provided in the shaft 2 are in communication with each other and with the outside by means of holes 11, through which a part of the pressurized air is discharged externally of the guide roll. As a result of the presence of this passage, the discharge of the pressurized fluid is improved, with the consequence that the load capacity of the bearing is increased.

As previously described, the flanges 3 and 7 are prov vided with a plurality of orifices 12. The total effective discharge area of these discharge orifices 12 should be 200 percent of the total area of the orifices 6.

According to our experiences, when the total effective discharge area of the orifices I2 is made about 40 percent of the total area of the orifices 6, it was confirmed that the amount of fluid discharged from the orifices 12 was insufficient, and hence the oscillations set up in the roll body 1 could not be checked. On the other hand, when the total effective discharge area of the orifices 12 is made about 230 percent, the amount of fluid discharged from the orifices 12 becomes excessive and likewise the oscillations set up in the roll body could not be checked. Hence, by maintaining the two areas in the foregoing range, it becomes possible to achieve a control of the oscillations as intended by the present invention without regard to the dimensions and configuration of the orifices, the magnitude of the clearances 8 and 9, the pressure of the pressurized fluid or the amount consumed of the pressurized fluid.

For more specifically illustrating the present invention, the following examples are given.

EXAMPLE 1 This example illustrates the instance where a bearing having a triple file air feed setup has been used, the various values of the bearing being as follows:

Total number of orifices 6 for introduction of pressurized air: n 12 X 3 36. Diameter of orifice 6: d 1.0 mm. Effective length of bearings:

Ll+L2+L3+L4+L5+L6 180 mm. Pressure of air fed: Ps ltg/cm absolute, Clearance in the radial direction between roll body 1 and shaft 2: C 40 X 10 mm.

Outside diameter of shaft 2: D 30 mm.

Number of discharge orifices 12: m 8 X 2 16.

Degree of effective discharge of the orifices l2: 4)

50 percent. Diameter of discharge orifices 12: d 2.5 mm. When the amount of air consumed (hereinafter abbreviated to Q Nl/min) and the radial load capacity (hereinafter abbreviated to W kg) were measured in this case, they were as follows:

Q 280 Nl/min and W 25 kg.

When the load capacity per unit amount of air consumed (hereinafter abbreviated to R) was calculated, it was R 25/280 0.089 kg-min/Nl.

Now, an R value of at least 0.04, as obtained by the foregoing method of calculation, is preferred. If the R value is less than this, the load capacity as compared with its amount of air consumed is small, and hence such a bearing has a very poor efficiency. Therefore, the bearing of the present example was deemed to be one of good efficiency. It is believed to be appropriate from the economic and performance standpoints to compare by means of the magnitude of such an R value the performance of the bearing portion which functions as an important part of the roll. When the P value, i.e., log n'd'L/Ps'C 'D, was calculated in this case, it was 4.4. Further, even when the filament guide roll part or the fittings were subjected to shocks, the guide roll was stable, there being no abnormal oscillations in the axial direction.

In this example, the ratio of the effective discharge area to the total area of the orifices 6 for introducing the pressurized air (hereinafter abbreviated to H value) was H 1r/4 -m (d) -/1r/4 n d 139 percent.

EXAMPLE 2 C= 25 X10 mm.

D mm.

m 8 X 2= 16 orifices.

50 percent.

d 3.6 mm.

When Q was measured in this case, Q 180 Nl/min. While the Q value was less than in the case of Example 1, a metal-to-metal rubbing contact occurred between the roll body 1 and the shaft 2, and hence it was impossible to obtain a load capacity in the radial direction. This is believed to have occurred because of the throttle resistance at the orifices 6 and the throttle resistance at the air film 8 being unbalanced. When the F value was calculated in this case, it was 5.01.

Further, it was confirmed in the case of this example that the roll body 1 oscillated in the axial direction when the roll fittings were subjected to a shock and that once the abnormal oscillations started the oscillations did not dampen but continued until the operation was stopped. During the continuance of the abnormal oscillations, the guide roll cannot be said to be a stable guide roll, since a metal-to-metal rubbing contact takes place in the axial direction. When the H value was calculated, it was 216 percent. It is believed that the oscillation controlling effect declined due to an excessive discharge of the pressurized air from the dishcarge -orifices 12.

EXAMPLE 3 In this example, there i is illustrated the instance where the guide roll used is one having the double file air feed setup. The dimensional values of the bearing design, etc., were as follows:

n= 6 X 2 =12 orifices.

d 0.8 mm.

Ps 5 kg/cm absolute.

C 40 X 10' mm.

D 20 mm.

m= 8 X 2= 16 orifices.

q) 50 percent.

When the Q and W values were measured in this case, they were as follows:

Q 60 Nl/min and W 4.2 kg.

in this case the R value was 0.070. Since R 0.04, this bearing can be regarded as being one having good efficiency.

The P value was 3.255. Further, the H value was 84 percent and there was no abnormal oscillations in the axial direction. And even though the fittings, r011 body, etc., were subjected to shocks, oscillations set up would promptly dampen and no troubles were noted. Further, since, as in Example 1, the flanges 3 and 7 at the two ends of the filament guide roll were provided with sleeves in the axial direction, as shown in H6. 5, the effect of preventing the entry of the filament into the clearance, as previously noted, was demonstrated even when the filament was being strung up or when break age of the filament took place. Thus, this guide roll was stable.

EXAMPLE 4 Another instance of a guide roll having the same type of double file air feed setup as in the case with Example 3 will be illustrated. The dimensional values of the 5 Q 170 Nl/min and W 4.6 kg.

When the R value was calculated, it was 0.027. The load capacity W increased somewhat, but since there was a still greater increase in the amount of air consumed, the R value declined.

In this example, it is believed that the poor efficiency, as above noted, of the bearing was due to the clearance C of the bearing being too great.

When the F value was calculated in this case, it was 1.963.

When the roll fittings were subjected to a shock as in Example 2, abnormal oscillations were set up in the roll body 1 in the axial direction. Hence, this guide roll could not be operated stably. When the H value was calculated, it was 43 percent. The amount of pressurized air discharged from the orifices 12 was insufficient, with the consequence that the oscillations in the roll body 1 in the axial direction could not be checked. Again, in contradistinction to the cases of Examples 1 and 3, sleeves 14 in the axial direction were not provided in this example. As a result, there were occasions when the filament would make entry into the clearance 9 during the stringing up of the filament or when breakage of the filament occurred to aggravate the operation characteristic of the guide roll to cause seizure of the bearing at times.

Example 5 This example will illustrate the instance of a guide roll having the single file air feed setup shown in FIG. 7.

n 6 X 1= 6 orifices.

d 0.8 mm.

L Ll+L2 7.5+7.5 15 mm.

Ps 4 kg/cm" absolute.

C 30 X 10' mm.

D 20 mm.

d1 50 percent.

d 0.65 mm.

When the Q and W values were measured in this case, they were as follows:

Q 18 Nl/ min and W 2.5 kg.

The R value in this case was 0.139. Since R 0.04, this bearing can be regarded as being efficient. The F value was 3.

Further, the H value being 88 percent, no oscillations in the axial direction were noted. Even though the fittings, roll body, etc., were subjected to shocks, the oscillations set up were promptly dempened.

EXAMPLE 6 Another instance of a guide roll having the same type of single file air feed setup as that of Example 5 will be illustrated.

n 6 X l= 6 orifices.

d 0.5 mm.

L Ll+L2 7.5+7.5 mm.

7 Ps 4 kg/cm absolute.

C 80 X 10 mm.

D mm.

m= 8 X 2 16 orifices.

percent.

d 0.65 mm.

When the Q and W values were measured in this case, they were as follows:

Q Nl/min and W 3.0 kg.

When the R value was calculated, it was 0.035. While there was a slight increase in the load capacity, there was a greater increase in the amount of air consumed, thus resulting in a decline of the R value.

In this example, the bearing was of poor efficiency, as indicated above, because of the excessive magnitude of the clearance C. When the F value was measured in this case, it was 1.944.

Further, when, as in the previous examples, the roll fitting was subjected a shock, there was set up in the roll body 1 abnormal oscillations in the axial direction. Hence, the guide roll in .this case was not stable.

When the H value was calculated, it was 225 percent. Hence, as a result of the discharge of an excessive amount of the pressurized air from the discharge orifices 12, the oscillation controlling effect had declined.

It is thus apparent from the foregoing examples that the guide roll of the present invention excels in its efficiency of load capacity per unit amount of air consumed, and hence is a roll that is stable economically and performance wise. Further, according to the present invention, when abnormal oscillations are set up in the roll body 1 in the axial direction and the end of the roll body 1 and the flange 7 come into contact to cause the clearance 9 to disappear, the pressurized air is not discharged from the clearance 9 but is discharged only from the discharge orifices 12 of the flange 7, since orifices 12 are provided on an extension line from the air film. In consequence, an abnormal rise in presuure takes place at the flange 7 side and, on the contrary, the pressure at the flange 3 side falls, with the consequence that the roll body 1 is pushed to return in the flange 3 direction. On the other hand, a similar phenomenon takes place when the end of the roll body 1 comes into contact with the flange 3 and the clearance 9 disappear at the flange 3 side, the roll body 1 thus being returned to the flange 7 side. As a result, it becomes possible to dampen the abnormal oscillations that have been set up and thus automatically return the guide roll to its normal state of operation.

Further, in accordance with the present invention, since sleeves 14 are provided in the axial direction in such a manner that the ends of the roll body 1 are en- 5 veloped, as hereinbefore described, the filament does not make entry into the clearance 9 even when breakage of the filament, etc., occur. Hence, a filament guide roll excelling in stability and operability can be provided. The entry of the filament into the clearance 13 between the roll body 1 and the sleeve 14 is more effectively prevented as the clerarance 13 becomes smaller, but if this clearance is too small, the act of throttling the discharge of the pressurized air takes place to cause a decline in the performance of the air bearing at the clearances 8 and 9. Hence, while the clearance 13 is to be determined as a result of various tests, in accordance with our experiences, the end can be achieved without preventing the discharge of the pressurized air and without impairing the effect of preventing the entry of the filament, if the clearance 13 is made of a magnitude several tens of times that of the bearing clearances 8 and 9. Further, it goes without saying that it is also possible to reduce the clearance 13 still more if the pressurized air, which has passed through the bearing clearance 9, is not discharged via the clearance 13 axially of the roll body 1 but is discharged radially of the roll body by providing, say, discharge orifices in the peripheral surface of the sleeve 14. Further, the sleeve 14 can fully demonstrate its effectiveness in preventing the entry of the filament if it overlaps the roll body 1 axially thereof for several millimeters. As apparent from what has been described so far, the present invention can be applied to all filament guide rolls which use orifices as the throttle, there being no restrictions imposed for the reason that the bearing used a single file or multifile air feed setup.

We claim:

1. A guide roll for filaments comprising a roll body fitted rotatably about a shaft, said shaft being provided with orifices through which pressurized air is intro duced to form between said roll body and said shaft an air film to thereby provide a bearing means by which the roll body is supported, characterized in that the various values involved in the design of said bearing means, are chosen such as to satisfy the following relationship:

wherein n is the total number of orifices for the introduction of the pressurized air, with the limitation that n g 6,

d is the diameter in millimeters of the orifices for introducing the pressurized air,

Ps is the pressure in kilograms per square centimeter absolute at which the pressurized air is fed, with the limitation that Rs 2 3,

C is the clearance in millimeters between the roll body and the shaft in the radial direction, with the limitation that C 10 X 10 D is the outside diameter in millimeters of the shaft,

and

L is the sum of the distances in millimeters from the several orifices to the pressurized air discharge outlet measured in the axial direction, provided that when there is no pressurized air outlet between adjace nt orifices, the distance between said orifices is not included.

2. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portion 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft.

3. In a guide roll according to claim 1, the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of which flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body 1.

4. In a guide roll according to claim 1, the provisions of flanges 3 and 7 at the ends of said shaft 2, said flanges being provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 200 percent of the area of said orifices 6.

5. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portions 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft, and moreover the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of said flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body 1.

6. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portions 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft, and moreover the provisions of flanges 3 and Tat the ends of said shaft 2, said flanges being provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 200 percent of the area of said orifices 6.

7. In a guide roll according to claim 1, the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of said flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body 1, said flanges 3 and 7 being further provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 200 percent of the area of said orifices 6.

8. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portions 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft, and moreover the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of said flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to-envelop the end of the roll body 1, said flanges being further provided with a plurality of fluid. discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge-oriflceslZ being 50 200 percent of the area of said orifices 6.

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1. A guide roll for filaments comprising a roll body fitted rotatably about a shaft, said shaft being provided with orifices through which pressurized air is introduced to form between said roll body and said shaft an air film to thereby provide a bearing means by which the roll body is supported, characterized in that the various values involved in the design of said bearing means, are chosen such as to satisfy the following relationship: 2 < log n.d.L/Ps.C2.D < 4.5 wherein n is the total number of orifices for the introduction of the pressurized air, with the limitation that n > OR = 6, d is the diameter in millimeters of the orifices for introducing the pressurized air, Ps is the pressure in kilograms per square centimeter absolute at which the pressurized air is fed, with the limitation that Ps > OR = 3, C is the clearance in millimeters between the roll body and the shaft in the radial direction, with the limitation that C > 10 X 10 3, D is the outside diameter in millimeters of the shaft, and L is the sum of the distances in millimeters from the several orifices to the pressurized air discharge outlet measured in the axial direction, provided that when there is no pressurized air outlet between adjacent orifices, the distance between said orifices is not included.
 2. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portion 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft.
 3. In a guide roll according to claim 1, the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of which flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body
 1. 4. In a guide roll according to claim 1, the provisions of flanges 3 and 7 at the ends of said shaft 2, said flanges being provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 -200 percent of the area of said orifices
 6. 5. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portions 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft, and moreover the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of said flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body
 6. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portions 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft, and moreover the provisions of flanges 3 and 7 at the ends of said shaft 2, said flanges being provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 -200 percent of the area of said orifices
 6. 7. In a guide roll according to claim 1, the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of said flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body 1, said flanges 3 and 7 being further provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 - 200 percent of the area of said orifices
 6. 8. In a guide roll according to claim 1, the provisions of one or more holes 11 disposed in said shaft 2 axially thereof, said holes communicating with recessed portions 10 provided inside said shaft 2 at points intermediately of said orifices 6, as well as with the outside of said shaft, and moreover the provisions of flanges 3 and 7 at the ends of said shaft 2, at least one of said flanges being provided with a sleeve 14 extending in the axial direction in such a manner as to envelop the end of the roll body 1, said flanges being further provided with a plurality of fluid discharge orifices 12 at positions on the extension line from the clearance 8, the effective discharge area of said discharge orifices 12 being 50 - 200 percent of the area of said orifices
 6. 